This combination weighing machine with a weight sensitive staggered discharge is an improvement upon combination weighing machines of the type generally described and claimed in commonly owned U.S. Pat. Nos. 4,630,695 and 4,901,807, the specifications and drawings of which are incorporated herein by reference.
When using a combination weighing machine of the type disclosed in the above referred to U.S. Pat. Nos. 4,630,695 and 4,901,807, a target package weight is preselected. Fractional amounts of the target package weight, which shall be referred to as product batches, are metered through a plurality of product batch handling units. Each separate product batch handling unit includes, in addition to other components, a radially extending product feeder trough, an accumulation chamber and a weighing device. The weighing device weighs the product batch that has been metered to it and records the weight; the weighed product batch is stored either in a weigh bucket associated with the weighing device or in a holding chamber disposed there below.
Some combination weighing machines discharge the selected product batches into a collecting hopper directly from the weigh bucket of each weighing device. Other combination weighing machines have a plurality of compartments, coinciding with each weighing device, that each store a product batch and from which the selected product batches are chosen. When a plurality of such compartments are used, they are referred to as holding chambers. The terms holding chamber or holding chambers, when used in this application, shall mean the compartment or compartments from which the product batches are fed to the collecting hopper.
The weight of the product batch that is metered to the weighing device can be controlled, for example by controlling the feed time for the conveying mechanism that meters out product to the product batch handling units. When a complete set of product batches has been weighed, recorded and stored, then combination weights are calculated and compared to the target package weight.
The term "best combination" as used in the combination weighing machine art and as used herein means the combination that best meets predefined specifications. The predefined specifications will be different for different products and can be inputted into the machine. For example a package that is stated to contain 8 ounces of product, may have predefined specifications as follows: Target weight equals 8 ounces, minus limits equals 0 ounces, and plus limit equals 1 ounce. With such predefined specifications the "best combination" would have a weight of at least 8 ounces but less than 9 ounces. If no combination fulfills these specifications then a machine signal is given.
It should be noted that in large combination weighing machines, there may be a population of many thousands of possible combinations. Some subsets within this population are very unlikely to include acceptable combinations and could be eliminated from consideration without affecting the results. Furthermore, it has been found that it is not necessary to generate the complete population of possible combinations to be assured of obtaining an acceptable combination. Also, the time required to generate the complete population of combinations slows the overall operation of the machine. In such situations, strategies can be developed to generate a subset of the complete population, with the assurance that an acceptable combination will be available. A best combination is then selected from the subset of generated combinations. The term "best combination" as used herein shall apply to such a combination even though not all possible combinations were generated.
A best combination, that fulfills the above criteria, is selected. The selected holding chambers are discharged into a collecting hopper for the formation of a package. The discharged holding chambers are then replenished and the cycle of selecting another acceptable combination is repeated. The discharge, of the selected holding chambers, into a collecting hopper can be done simultaneously or it can be staggered.
Prior art combination weighing machines are of two general types, in-line and radial. The in-line type machines have the weighing devices arranged side by side along a line. The radial type machines have the weighing devices arranged around a circle. Both of the above identified U.S. Pat. Nos. 4,630,695 and 4,901,807 disclose in-line type combination weighing machines. U.S. Pat. No. 4,901,807 also discloses a radial type combination weighing machine.
Combination weighing machines frequently have a funnel shaped collecting hopper disposed so as to receive the combination of product batches having the target weight. All discharged product batches travel substantially the same distance to the outlet of such a funnel shaped collecting hopper. This can result in product jams, bridging or blocking at the outlet. By staggering the discharges of the product batches, such that all batches do not converge on the collecting hopper at the same time, the likelihood of blockages can be reduced. Staggered discharge is known in the prior art. However, available staggered discharge systems have not completely resolved the problem. Current combination weighing machines can produce more than 100 discrete quantities of product per minute. Thus, the total discharge time that is available for the product of one package is but a fraction of a second. As a result, even with a staggered discharge, product batches may overlap in flowing through the outlet of the collecting hopper, and result in blockages.
Heretofore, it has been known to use plural net weighing machines to produce packages that include two or more different ingredients. In packaging systems of this type, each net weighing machine weighed out a batch of a single ingredient and the machine was programmed to discharge its individual batches in predetermined, timed sequence into a common collecting hopper. In some such machines, it was desired that the different ingredients be layered in the package; in others, the denser ingredient was deposited at the top of the product and was expected to disperse itself downwardly throughout the less dense ingredient below it; while in others, the final discharge into the package was a dribble feed to top off the package to its target weight.
The sequential discharge of product batches is also old in the combination weighing machine prior art U.S. Pat. No. 4,385,671 discloses a combination weighing machine. In the preferred embodiment of this patent, the selected batches are discharged simultaneously into a collecting hopper; however, in another embodiment, the selected batches are indicated by pilot lamps and an operator manually unloads the selected batches sequentially rather than simultaneously. U.S. Pat. Nos. 4,467,880 and 4,574,897 also disclose combination weighing machines having sequential discharge of the selected batches of product. However, none of these prior art combination weighing machines discloses the concepts of ordering or timing the sequential discharge on the basis of the weights of the selected batches.
It is a primary objective of the present invention to provide a combination weighing machine that is more reliable as a result of having a weight sensitive sequential discharge of the product batches making up the total package.
Another primary objective of the present invention is to provide a combination weighing machine that is more reliable as a result of the timing between discharges being weight sensitive.
Still another primary objective of the present invention is to provide a combination weighing machine that is more reliable as a result of having a weight sensitive sequential discharge in combination with the timing between discharges being weight sensitive.
Another objective of the present invention is to reduce the total time required to discharge the selected batches by discharging the batches sequentially in a weight sensitive order with either an equal or variable time delay for each batch.
Still another objective of the present invention is to increase the efficiency of present combination weighing machines by discharging the selected batches into a collecting hopper in an order based upon the weight of the selected batches.